The cost of energy to operate an industrial refrigerator that consumes 5 kW power working 10 hours per day for 30 days will be (Given that the charge per kW.h of energy = ₹ 4)
- A.₹ 600
- B.₹ 6,000
- C.₹ 1,200
- D.₹ 1,500
Correct answer
Explanation
The correct answer is B, ₹ 6,000. The refrigerator uses 5 kW × 10 h × 30 days = 1,500 kWh, and at ₹ 4 per kWh that costs ₹ 6,000.
Electrical energy equals power multiplied by time. In one day the refrigerator uses 5 kW × 10 h = 50 kWh. Over 30 days it uses 50 × 30 = 1,500 kWh. One kilowatt-hour is the commercial unit of electrical energy, the familiar unit on an electricity bill, and it equals 3.6 × 10^6 joules. The bill is the number of units multiplied by the rate: 1,500 × ₹ 4 = ₹ 6,000.
A is wrong because ₹ 600 is the cost of only 150 kWh, which is the use for three days.
C is wrong because ₹ 1,200 matches 300 kWh, which ignores most of the running time.
D is wrong because 1,500 is the number of units used, not their cost in rupees.
Exam tip: energy (kWh) = power (kW) × hours; cost = units × rate; 1 kWh = 1 unit = 3.6 × 10^6 J.
Practice Questions
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Show answer
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Show answer
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Show answer
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